1997 SLK 230k auto. Missfire after 1800rpm

[slippy]

Hi, I have my first real problem with my SLK, its got me (& others) stumped! This is my toy & doesnt come out often.

I replaced the cam sensor magnet with a genuine one from Mercedes & fitted it with the genuine Merc sealant as I had a slight weep of oil from it. The electrical plug that fits onto it was slightly damaged, so this was replaced & the breather pipe on top of the engine was also split, this was replaced too.

Once the above parts were fitted I started the car & all seemed well.
A few weeks later, I started the car & all seemed well again, I reversed it out of the garage, no problems. I set off down the road & once upto about 1800 revs, it felt like it was running on 3 cylinders.
I didn't have time to do anything so put it back in the garage. Checked again a few days later & it started fine, reversed out fine, set off & same thing happened. The same fault occurs even if the car is in PARK & you gently increase the revs to about 1800rpm.

I had the codes read & it showed a missfire on cylinders 3 & 4 so I replaced the plugs, coil packs & plug leads. I also cleaned the MAF with electrical solvant cleaner. The codes were cleared & tried again. The car starts up perfect, ticks over fine but as soon as the car hits a certain amount of revs the missfire happens again. If you stop the engine & immediately start it again, its fine untill you set off?


I cant drive the car to a garage so Ive had an auto electrician out who read the codes, he checked the feed to the coils & said they were ok.

I cant drive it to a garage & I have since thrown away the old cam sensor magnet so I cant re fit that.......Any ideas please??

 

[streethawk]

Hi, I have my first real problem with my SLK, its got me (& others) stumped! This is my toy & doesnt come out often.

I replaced the cam sensor magnet with a genuine one from Mercedes & fitted it with the genuine Merc sealant as I had a slight weep of oil from it. The electrical plug that fits onto it was slightly damaged, so this was replaced & the breather pipe on top of the engine was also split, this was replaced too.

Once the above parts were fitted I started the car & all seemed well.
A few weeks later, I started the car & all seemed well again, I reversed it out of the garage, no problems. I set off down the road & once upto about 1800 revs, it felt like it was running on 3 cylinders.
I didn't have time to do anything so put it back in the garage. Checked again a few days later & it started fine, reversed out fine, set off & same thing happened. The same fault occurs even if the car is in PARK & you gently increase the revs to about 1800rpm.

I had the codes read & it showed a missfire on cylinders 3 & 4 so I replaced the plugs, coil packs & plug leads. I also cleaned the MAF with electrical solvant cleaner. The codes were cleared & tried again. The car starts up perfect, ticks over fine but as soon as the car hits a certain amount of revs the missfire happens again. If you stop the engine & immediately start it again, its fine untill you set off?

I cant drive the car to a garage so Ive had an auto electrician out who read the codes, he checked the feed to the coils & said they were ok.

I cant drive it to a garage & I have since thrown away the old cam sensor magnet so I cant re fit that.......Any ideas please??

Hi it does sound like the maf. Was it covered in oil before you cleaned it? Some say don't clean them but my old one was toast so cleaning made no improvement. New one got contaminated as had residue oil in supercharger because that's the only place I didn't clean out after unblocking breathers under inlet manifold. Clean new one and let dry in the air and never had another problem touch wood.

 

[BlackC55]

I would say its a maf issue too.

There will be codes. It wont say the maf is the issue, just a mixture problem. Cleaning it is a waste of time as it can often make matters worse.

 

[slippy]

Hi, thank you very much for your quick replies.
Im obviously no expert but I dont think its the MAF as its a very serious missfire, not just running a bit rough. There was no oily deposits on the MAF & very little oil in the intercooler pipework, I just gave it a light spray of cleaner as a last resort.
I had a MGZT with a faulty MAF & it feels nothing like that, unless ofcourse a faulty MAF can cause two cylinders to shut down? I tried disconnecting the MAF as sometimes this can make things improve. There was no change when I dud this.
The only fault codes were missfire on cylinders 2 & 3.

 

[BlackC55]

Still could be the maf!

Get it on a Star to confirm.

 

[flango]

MAF's on Kompressor engines do funny things sometimes you wont see the codes for a MAF fault even on Star but its the usual cause from what you say its either the MAF or coil packs I'd say. I know the coil packs aren't showing codes but are you sure they are good? even new ones have been known to be faulty. Anyway can you can borrow a working MAF from a local members car and swap it over this would eliminate the MAF also check the kompressor air circuits for faults leaks as this is also known to cause misfires on this engine, good luck

 

[slippy]

MAF's on Kompressor engines do funny things sometimes you wont see the codes for a MAF fault even on Star but its the usual cause from what you say its either the MAF or coil packs I'd say. I know the coil packs aren't showing codes but are you sure they are good? even new ones have been known to be faulty. Anyway can you can borrow a working MAF from a local members car and swap it over this would eliminate the MAF also check the kompressor air circuits for faults leaks as this is also known to cause misfires on this engine, good luck

Thanks for your reply.
I dont know anyone with an SLK so cant borrow any parts unfortunately. Last night I swapped all the coil packs around, I have the two original ones & the two brand new ones, no difference.............had a thought though. They didnt come with new rubber boot things that go down to the spark plugs so going to get new ones today hopefully.

 

[slippy]

Ive had another look around & still no wiser.

I removed the K40 PCB & all looks well. All the solder looks like nice shiney blobs of silver, no pitting or corrosion or cracks that I can see.

I bought 2 x new spark plug conector boots that fit on the coil packs as I had not replaced these. I also swapped all the coil packs around, trying the old ones again & then one old & one new in different positions, no change.

I checked the hoses & hose clips for splits & air leaks.....nothing

 

[BlackC55]

FFS! Stop throwing parts at it!! Get it diagnosed properly and you will find the cause.

Which will be a faulty MAF I suspect.

 

[slippy]

Im taking it in tomorrow...I took the Jag in for its MOT yesterday to my local garage & was talking to them about the Merc & they told me of a local "German car specialist" that is only about a mile & half away. I went in to see him, he had a Z4 & a Boxster in at the time.
I told him of the problem & Im going to have a very steady drive to him tomorrow afternoon after work. Im going to leave it with him to have a look.

Jag passed with no advisories by the way

 

[slippy]

Well the guy has pulled codes that the auto electrician did not get. These are P0341 & P1525 ......as well as the previous missfire codes.

Before he plugged in he was convinced it was a blocked cat but nope.

He now says its a faulty camshaft sensor?

 

[Sp!ke]

Could be camshaft sensor or camshaft timing solenoid.

Mercedes-Benz Forum - View Single Post - '97 E320 P1525

Could be that the connectors need a clean.

 

[slippy]

Well, not much to report. The car is still not fixed but I thought I better update just incase anyone else gets the same fault.

A new camshaft sensor was fitted, no change so he claims he had the car taken to a friend of his who has STAR. He had it for a few hours but does not know the cause of the fault. I am going to collect the car from him on Saturday & bring it home till I figure out what next. He says the STAR guy says the MAF is fine?

Really dont know where to go from here as I dont know of a local indi near by & now the MOT & Tax has expired.

 

[Remote11]

Hi mine is doing the exact same thing totally different engine exact same symptoms.....I have asked another member on here for his local indi as he is not far from me hoping to get to the bottom of it before I shell out...just got to get it to him first as its very hard to get it to drive , if I have any luck before you do I will let you know

 

[slippy]

Well I hope you have better luck than me with it mate.
It is horrible to try to drive, only drove it about a mile & half to the garage all down hill, god knows how Im goin to get it back home.
Thing I cant get my head round is as soon as you turn it off, its all fine again.

 

[Remote11]

I know mine is the same feels like the engine is going to shake it self to bits when it happens....I had to drive it 4 miles home the other day, utter mission when you can't stop to re start..if that makes sense...I found getting it rolling then just feather the pedal to get momentum helps, but like you say when it is first started it's silky smooth ..on mine though the BAS/ASR light can come on sometimes then the engine shake starts...even if it is sat on the drive and not moved any were so I am stabbing in the dark that it may be something to do with the ASR side of things....again just guessing for now......bring back cables and bloody levers I say!!

 

[Remote11]

and by engine shake I mean when the misfire starts....sounds like only 2 cylinders firing its that bad

 

[slippy]

Exactly!
Mine is firing on 2 cylinders when the fault occurs. Codes say missfire on cylinders 2 & 3. I have no lights lit on the dash though.

 

[BlackC55]

Get it plugged into a Star firstly. It will be a guessing game if you don't.

 

[Remote11]

Hi well I have today borrowed a known working MAF....still got the issue..so not that